api.md revision 262975
1Synopsis 2======== 3 4`#include <ucl.h>` 5 6Description 7=========== 8 9Libucl is a parser and `C` API to parse and generate `ucl` objects. Libucl consist of several groups of functions: 10 11### Parser functions 12Used to parse `ucl` files and provide interface to extract `ucl` object 13 14### Emitting functions 15Convert `ucl` objects to some textual or binary representation. 16 17### Conversion functions 18Help to convert `ucl` objects to C types 19 20### Generation functions 21Allow creating of `ucl` objects from C types 22 23### Iteration functions 24Iterate over `ucl` objects 25 26### Utility functions 27Provide basic utilities to manage `ucl` objects 28 29# Parser functions 30 31Parser functions operates with `struct ucl_parser`. 32 33### ucl_parser_new 34 35~~~C 36struct ucl_parser* ucl_parser_new (int flags); 37~~~ 38 39Creates new parser with the specified flags: 40 41- `UCL_PARSER_KEY_LOWERCASE` - lowercase keys parsed 42- `UCL_PARSER_ZEROCOPY` - try to use zero-copy mode when reading files (in zero-copy mode text chunk being parsed without copying strings so it should exist till any object parsed is used) 43 44### ucl_parser_register_macro 45 46~~~C 47void ucl_parser_register_macro (struct ucl_parser *parser, 48 const char *macro, ucl_macro_handler handler, void* ud); 49~~~ 50 51Register new macro with name .`macro` parsed by handler `handler` that accepts opaque data pointer `ud`. Macro handler should be of the following type: 52 53~~~C 54bool (*ucl_macro_handler) (const unsigned char *data, 55 size_t len, void* ud);` 56~~~ 57 58Handler function accepts macro text `data` of length `len` and the opaque pointer `ud`. If macro is parsed successfully the handler should return `true`. `false` indicates parsing failure and the parser can be terminated. 59 60### ucl_parser_register_variable 61 62~~~C 63void ucl_parser_register_variable (struct ucl_parser *parser, 64 const char *var, const char *value); 65~~~ 66 67Register new variable $`var` that should be replaced by the parser to the `value` string. 68 69### ucl_parser_add_chunk 70 71~~~C 72bool ucl_parser_add_chunk (struct ucl_parser *parser, 73 const unsigned char *data, size_t len); 74~~~ 75 76Add new text chunk with `data` of length `len` to the parser. At the moment, `libucl` parser is not a streamlined parser and chunk *must* contain the *valid* ucl object. For example, this object should be valid: 77 78~~~json 79{ "var": "value" } 80~~~ 81 82while this one won't be parsed correctly: 83 84~~~json 85{ "var": 86~~~ 87 88This limitation may possible be removed in future. 89 90### ucl_parser_add_file 91 92~~~C 93bool ucl_parser_add_file (struct ucl_parser *parser, 94 const char *filename); 95~~~ 96 97Load file `filename` and parse it with the specified `parser`. This function uses `mmap` call to load file, therefore, it should not be `shrinked` during parsing. Otherwise, `libucl` can cause memory corruption and terminate the calling application. This function is also used by the internal handler of `include` macro, hence, this macro has the same limitation. 98 99### ucl_parser_get_object 100 101~~~C 102ucl_object_t* ucl_parser_get_object (struct ucl_parser *parser); 103~~~ 104 105If the `ucl` data has been parsed correctly this function returns the top object for the parser. Otherwise, this function returns the `NULL` pointer. The reference count for `ucl` object returned is increased by one, therefore, a caller should decrease reference by using `ucl_object_unref` to free object after usage. 106 107### ucl_parser_get_error 108 109~~~C 110const char *ucl_parser_get_error(struct ucl_parser *parser); 111~~~ 112 113Returns the constant error string for the parser object. If no error occurred during parsing a `NULL` object is returned. A caller should not try to free or modify this string. 114 115### ucl_parser_free 116 117~~~C 118void ucl_parser_free (struct ucl_parser *parser); 119~~~ 120 121Frees memory occupied by the parser object. The reference count for top object is decreased as well, however if the function `ucl_parser_get_object` was called previously then the top object won't be freed. 122 123### ucl_pubkey_add 124 125~~~C 126bool ucl_pubkey_add (struct ucl_parser *parser, 127 const unsigned char *key, size_t len); 128~~~ 129 130This function adds a public key from text blob `key` of length `len` to the `parser` object. This public key should be in the `PEM` format and can be used by `.includes` macro for checking signatures of files included. `Openssl` support should be enabled to make this function working. If a key cannot be added (e.g. due to format error) or `openssl` was not linked to `libucl` then this function returns `false`. 131 132### ucl_parser_set_filevars 133 134~~~C 135bool ucl_parser_set_filevars (struct ucl_parser *parser, 136 const char *filename, bool need_expand); 137~~~ 138 139Add the standard file variables to the `parser` based on the `filename` specified: 140 141- `$FILENAME` - a filename of `ucl` input 142- `$CURDIR` - a current directory of the input 143 144For example, if a `filename` param is `../something.conf` then the variables will have the following values: 145 146- `$FILENAME` - "../something.conf" 147- `$CURDIR` - ".." 148 149if `need_expand` parameter is `true` then all relative paths are expanded using `realpath` call. In this example if `..` is `/etc/dir` then variables will have these values: 150 151- `$FILENAME` - "/etc/something.conf" 152- `$CURDIR` - "/etc" 153 154## Parser usage example 155 156The following example loads, parses and extracts `ucl` object from stdin using `libucl` parser functions (the length of input is limited to 8K): 157 158~~~C 159char inbuf[8192]; 160struct ucl_parser *parser = NULL; 161int ret = 0, r = 0; 162ucl_object_t *obj = NULL; 163FILE *in; 164 165in = stdin; 166parser = ucl_parser_new (0); 167while (!feof (in) && r < (int)sizeof (inbuf)) { 168 r += fread (inbuf + r, 1, sizeof (inbuf) - r, in); 169} 170ucl_parser_add_chunk (parser, inbuf, r); 171fclose (in); 172 173if (ucl_parser_get_error (parser)) { 174 printf ("Error occured: %s\n", ucl_parser_get_error (parser)); 175 ret = 1; 176} 177else { 178 obj = ucl_parser_get_object (parser); 179} 180 181if (parser != NULL) { 182 ucl_parser_free (parser); 183} 184if (obj != NULL) { 185 ucl_object_unref (obj); 186} 187return ret; 188~~~ 189 190# Emitting functions 191 192Libucl can transform UCL objects to a number of tectual formats: 193 194- configuration (`UCL_EMIT_CONFIG`) - nginx like human readable configuration file where implicit arrays are transformed to the duplicate keys 195- compact json: `UCL_EMIT_JSON_COMPACT` - single line valid json without spaces 196- formatted json: `UCL_EMIT_JSON` - pretty formatted JSON with newlines and spaces 197- compact yaml: `UCL_EMIT_YAML` - compact YAML output 198 199Moreover, libucl API allows to select a custom set of emitting functions allowing 200efficent and zero-copy output of libucl objects. Libucl uses the following structure to support this feature: 201 202~~~C 203struct ucl_emitter_functions { 204 /** Append a single character */ 205 int (*ucl_emitter_append_character) (unsigned char c, size_t nchars, void *ud); 206 /** Append a string of a specified length */ 207 int (*ucl_emitter_append_len) (unsigned const char *str, size_t len, void *ud); 208 /** Append a 64 bit integer */ 209 int (*ucl_emitter_append_int) (int64_t elt, void *ud); 210 /** Append floating point element */ 211 int (*ucl_emitter_append_double) (double elt, void *ud); 212 /** Opaque userdata pointer */ 213 void *ud; 214}; 215~~~ 216 217This structure defines the following callbacks: 218 219- `ucl_emitter_append_character` - a function that is called to append `nchars` characters equal to `c` 220- `ucl_emitter_append_len` - used to append a string of length `len` starting from pointer `str` 221- `ucl_emitter_append_int` - this function applies to integer numbers 222- `ucl_emitter_append_double` - this function is intended to output floating point variable 223 224The set of these functions could be used to output text formats of `UCL` objects to different structures or streams. 225 226Libucl provides the following functions for emitting UCL objects: 227 228### ucl_object_emit 229 230~~~C 231unsigned char *ucl_object_emit (ucl_object_t *obj, enum ucl_emitter emit_type); 232~~~ 233 234Allocate a string that is suitable to fit the underlying UCL object `obj` and fill it with the textual representation of the object `obj` according to style `emit_type`. The caller should free the returned string after using. 235 236### ucl_object_emit_full 237 238~~~C 239bool ucl_object_emit_full (ucl_object_t *obj, enum ucl_emitter emit_type, 240 struct ucl_emitter_functions *emitter); 241~~~ 242 243This function is similar to the previous with the exception that it accepts the additional argument `emitter` that defines the concrete set of output functions. This emit function could be useful for custom structures or streams emitters (including C++ ones, for example). 244 245# Conversion functions 246 247Conversion functions are used to convert UCL objects to primitive types, such as strings, numbers or boolean values. There are two types of conversion functions: 248 249- safe: try to convert an ucl object to a primitive type and fail if such a conversion is not possible 250- unsafe: return primitive type without additional checks, if the object cannot be converted then some reasonable default is returned (NULL for strings and 0 for numbers) 251 252Also there is a single `ucl_object_tostring_forced` function that converts any UCL object (including compound types - arrays and objects) to a string representation. For compound and numeric types this function performs emitting to a compact json format actually. 253 254Here is a list of all conversion functions: 255 256- `ucl_object_toint` - returns `int64_t` of UCL object 257- `ucl_object_todouble` - returns `double` of UCL object 258- `ucl_object_toboolean` - returns `bool` of UCL object 259- `ucl_object_tostring` - returns `const char *` of UCL object (this string is NULL terminated) 260- `ucl_object_tolstring` - returns `const char *` and `size_t` len of UCL object (string can be not NULL terminated) 261- `ucl_object_tostring_forced` - returns string representation of any UCL object 262 263Strings returned by these pointers are associated with the UCL object and exist over its lifetime. A caller should not free this memory. 264 265# Generation functions 266 267It is possible to generate UCL objects from C primitive types. Moreover, libucl permits to create and modify complex UCL objects, such as arrays or associative objects. 268 269## ucl_object_new 270~~~C 271ucl_object_t * ucl_object_new (void) 272~~~ 273 274Creates new object of type `UCL_NULL`. This object should be released by caller. 275 276## ucl_object_typed_new 277~~~C 278ucl_object_t * ucl_object_typed_new (unsigned int type) 279~~~ 280 281Create an object of a specified type: 282- `UCL_OBJECT` - UCL object - key/value pairs 283- `UCL_ARRAY` - UCL array 284- `UCL_INT` - integer number 285- `UCL_FLOAT` - floating point number 286- `UCL_STRING` - NULL terminated string 287- `UCL_BOOLEAN` - boolean value 288- `UCL_TIME` - time value (floating point number of seconds) 289- `UCL_USERDATA` - opaque userdata pointer (may be used in macros) 290- `UCL_NULL` - null value 291 292This object should be released by caller. 293 294## Primitive objects generation 295Libucl provides the functions similar to inverse conversion functions called with the specific C type: 296- `ucl_object_fromint` - converts `int64_t` to UCL object 297- `ucl_object_fromdouble` - converts `double` to UCL object 298- `ucl_object_fromboolean` - converts `bool` to UCL object 299- `ucl_object_fromstring` - converts `const char *` to UCL object (this string is NULL terminated) 300- `ucl_object_fromlstring` - converts `const char *` and `size_t` len to UCL object (string can be not NULL terminated) 301 302Also there is a function to generate UCL object from a string performing various parsing or conversion operations called `ucl_object_fromstring_common`. 303 304## ucl_object_fromstring_common 305~~~C 306ucl_object_t * ucl_object_fromstring_common (const char *str, 307 size_t len, enum ucl_string_flags flags) 308~~~ 309 310This function is used to convert a string `str` of size `len` to an UCL objects applying `flags` conversions. If `len` is equal to zero then a `str` is assumed as NULL-terminated. This function supports the following flags (a set of flags can be specified using logical `OR` operation): 311 312- `UCL_STRING_ESCAPE` - perform JSON escape 313- `UCL_STRING_TRIM` - trim leading and trailing whitespaces 314- `UCL_STRING_PARSE_BOOLEAN` - parse passed string and detect boolean 315- `UCL_STRING_PARSE_INT` - parse passed string and detect integer number 316- `UCL_STRING_PARSE_DOUBLE` - parse passed string and detect integer or float number 317- `UCL_STRING_PARSE_NUMBER` - parse passed string and detect number (both float or integer types) 318- `UCL_STRING_PARSE` - parse passed string (and detect booleans and numbers) 319- `UCL_STRING_PARSE_BYTES` - assume that numeric multipliers are in bytes notation, for example `10k` means `10*1024` and not `10*1000` as assumed without this flag 320 321If parsing operations fail then the resulting UCL object will be a `UCL_STRING`. A caller should always check the type of the returned object and release it after using. 322 323# Iteration function 324 325Iteration are used to iterate over UCL compound types: arrays and objects. Moreover, iterations could be performed over the keys with multiple values (implicit arrays). To iterate over an object, an array or a key with multiple values there is a function `ucl_iterate_object`. 326 327## ucl_iterate_object 328~~~C 329ucl_object_t* ucl_iterate_object (ucl_object_t *obj, 330 ucl_object_iter_t *iter, bool expand_values); 331~~~ 332 333This function accept opaque iterator pointer `iter`. In the first call this iterator *must* be initialized to `NULL`. Iterator is changed by this function call. `ucl_iterate_object` returns the next UCL object in the compound object `obj` or `NULL` if all objects have been iterated. The reference count of the object returned is not increased, so a caller should not unref the object or modify its content (e.g. by inserting to another compound object). The object `obj` should not be changed during the iteration process as well. `expand_values` flag speicifies whether `ucl_iterate_object` should expand keys with multiple values. The general rule is that if you need to iterate throught the *object* or *explicit array*, then you always need to set this flag to `true`. However, if you get some key in the object and want to extract all its values then you should set `expand_values` to `false`. Mixing of iteration types are not permitted since the iterator is set according to the iteration type and cannot be reused. Here is an example of iteration over the objects using libucl API (assuming that `top` is `UCL_OBJECT` in this example): 334 335~~~C 336ucl_object_iter_t it = NULL, it_obj = NULL; 337ucl_object_t *cur, *tmp; 338 339/* Iterate over the object */ 340while ((obj = ucl_iterate_object (top, &it, true))) { 341 printf ("key: \"%s\"\n", ucl_object_key (obj)); 342 /* Iterate over the values of a key */ 343 while ((cur = ucl_iterate_object (obj, &it_obj, false))) { 344 printf ("value: \"%s\"\n", 345 ucl_object_tostring_forced (cur)); 346 } 347} 348~~~